"I love India which is why we came back to visit," Keith told the Associated Press, explaining he had studied in India years ago. "We have heard about the growing Hindu nationalism, but nothing justifies the way we were treated," he added.

India has seen a rise in incidents of religious intolerance over the past year, with Hindu nationalists trying to create a more Hindu-centric country.

Keith said he also had a tattoo of the elephant-headed Hindu god Ganesha on his back.

Keith said he did not think he had done anything wrong.

"I should not have to apologize for what is on my skin and be put in a traumatizing situation where it is apparently acceptable to be harassed, threatened and mobbed," he wrote on Facebook.

Bangalore's deputy commissioner of police said Monday that an investigation had been ordered into the incident and its handling by local police.

"If police forced the couple to give an apology, it is a serious matter," Sandeep Patil told reporters.